The generation of high-intensity attosecond pulses by the interaction of two counterpropagating short laser pulses with underdense plasma is investigated. By using parallel fully kinetic particles in cell simulation, which shows the formation of relativistic flying mirrors in the wake wave of the intense driver laser pulse and the focusing reflection of the weak source pulse, it is demonstrated that intense attosecond pulses can be produced under the optimized conditions of plasma density and driver laser amplitude according to the relativistic similarity theory. In addition, it is shown that the frequency of the source pulse is upshifted by a factor from 10 to 80 corresponding to a reflected radiation wavelength from 20 to 164 nm which lies in the extreme ultraviolet region, while most of the energy lies around a frequency upshift of 20, in agreement with the measured Lorentz factor. The intensity of the main attosecond pulse is two orders higher than the source pulse intensity.
The attosecond pulse generation by the interaction of two counterpropagating ultrashort laser pulses with near-critical density plasma is simulated using two-dimensional particle in the cell method. Results of the simulations showed the flying mirror properties such as density and shape change, while moving through the plasma, behind the intense driver laser. We investigated the effects of the mirror features on the produced attosecond pulse intensity by setting various delay times between the driver and source pulses so that the source encounters the mirror at different points. It is demonstrated that the higher density of the mirror, particularly in its center (due to the Gaussian transverse profile of the source), in addition to its suitable curvature and surface smoothness, results in a more intense reflection. Moreover, a considerable size of the hole created in the mirror center due to the self-injection process has a destructive effect on the reflection efficiency. Finally, an efficient reflection can be obtained by controlling the delay time. The optimal delay for arbitrary parameters of the laser and plasma depends on the region in which the most efficient flying mirrors are created by the mutual interaction of the plasma density and the driver amplitude along with considering the pulse situation when reaching the mirror. By analyzing the electron phase space, it was found that the velocity of density spikes changes rapidly when passing through the plasma. The higher speed of the electrons of the mirrors contributing to the source reflection leads to the production of the higher upshifted frequency peak in different source delays.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.